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TRAILING EDGE FLAPS -FUNCTIONAL DESCRIPTION -SECONDARY MODE CONTROL
Cruise Inhibit
This function prevents flap extension during cruise. This happens when the airspeed is more than 250 knots or the altitude is above 20,300 feet.
Secondary Mode Auto Test
The secondary mode auto test checks the operation of the secondary mode. After 100 flight cycles, the FSEUs begin the test when the flaps are commanded to extend. The test does the following:
*
Disengages the primary mode
*
Engages the electric motor clutch
*
Extends the flaps for two seconds using the electric motor.
One flight cycle is when all of these conditions occur for two seconds:
*
Airplane not on the ground
*
Airspeed is greater than 70 knots
*
Flap lever is at up
*
Flaps are at up.
If the flaps fail to extend during the secondary mode auto test, the FLAPS SECONDARY FAIL status message shows.
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TRAILING EDGE FLAPS -FUNCTIONAL DESCRIPTION -ALTERNATE MODE CONTROL
General
The alternate mode operation of the flaps is almost the same as the alternate mode operation of the slats.
See the leading edge slats section for more information about the slats alternate mode control (SECTION 27-81).
In the alternate mode, the alternate flap/slat switches energize relays. The relays control the electrical power to the electric motor, clutch, and bypass solenoid.
In the alternate mode, these functions occur:
*
Primary and secondary mode disengage
*
Extend and retract control
*
Flap/slat sequence.
Primary and Secondary Mode Disengage
When you push the alternate flaps arm switch, the FSEUs receive an alternate arm discrete. The FSEUs use this discrete to disengage the primary and secondary modes.
The alternate flaps arm switch also supplies a ground for the bypass/clutch relay. The operation of the bypass/clutch relay in the alternate mode is the same as in the secondary mode.
Extend and Retract Control
When the alternate flaps selector is in the extend (EXT) position, it supplies a ground for the extend relay to extend the flaps. When this relay energizes, it supplies 115v ac power to the electric motor. The flap limit switch de-energizes this relay when the flaps move to their extend limit. In the alternate mode, this limit is at the flap 20 position.
When the alternate flaps selector is in the retract (RET) position, it supplies a ground for the retract relay to retract the flaps. When this relay energizes, it supplies 115v ac power to the electric motor. The flap limit switch de-energizes this relay when the flaps move to the up position.
When the alternate flaps selector is in the off position, the grounds for the extend and retract relays is removed. This de-energizes the relays and stops the flap movement.
Flap/Slat Sequence
During extension, both the flaps and slats extend at the same time.
During retraction, the flap limit switch prevents retraction of the slats until the flaps are fully retracted.
See the high lift control section for more information about the alternate mode flap and slat sequence (SECTION 27-03).
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777 AIRCRAFT MAINTENANCE MANUAL
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BOEING PROPRIETARY -Copyright # -Unpublished Work -See title page for details.
FLAP POSITION INDICATION -GENERAL DESCRIPTION
Purpose
The flap position indication system measures the position of the flaps and sends this data to the FSEUs. The FSEUs use this data for:
*
Flap control
*
Flap/slat position indication
*
Failure detection.
Flap Control
The FSEUs use the flap position data during the flap operation in the primary and secondary modes. These modes have closed loop control of the flaps. Closed-loop control stops the flap command when the flap position equals the command.
Flap/Slat Position Indication
The FSEUs send the flap position data to the airplane information management system (AIMS). The AIMS uses this data to show the flap/slat position indication on the EICAS display or the EICAS compacted engine display. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：777 AMM 飞机维护手册 飞行操纵 Flight Controls 2(43)
